downgrading from 39 to 12
My OS is Ubuntu 16.04.
I'd like to downgrade back to opera12. I have tried 39 but it does not work well for me
What is the best way to downgrade back to 12?
To downgrade is not a good idea, Opera 12 is a very old version, it's like you would install Google Chrome 20 from 2012.
However, you run Opera 12 by the side of an existing Opera installation by downloading the tar.xz file for your architecture from here: http://ftp.opera.com/pub/opera/linux/1216/. Then you can just extract and run it.
I don't know of any way to downgrade except for uninstalling and installing, which may not keep the data from the previous version or be compatible with it.